3GPP LTE employs Orthogonal Frequency Division Multiple Access (OFDMA) as a downlink communication scheme. In radio communication systems to which 3GPP LTE is applied, base stations transmit synchronization signals (i.e., Synchronization Channel: SCH) and broadcast signals (i.e. Broadcast Channel: BCH) using predetermined communication resources. Meanwhile, each terminal finds an SCH first and thereby ensures synchronization with the base station. Subsequently, the terminal reads BCH information to acquire base station-specific parameters (see, Non-Patent Literature (hereinafter, abbreviated as NPL) 1, 2 and 3).
In addition, upon completion of the acquisition of the base station-specific parameters, each terminal sends a connection request to the base station to thereby establish a communication link with the base station. The base station transmits control information via a downlink control channel, such as Physical Downlink Control CHannel (PDCCH), as appropriate, to the terminal with which a communication link has been established.
The terminal performs “blind-determination” on each of a plurality of control information items included in the received PDCCH signal (i.e., Downlink (DL) Assignment Control Information: also referred to as Downlink Control Information (DCI)). To put it more specifically, each of the control information items includes a Cyclic Redundancy Check (CRC) part and the base station masks this CRC pert using the terminal ID of the transmission target terminal. Accordingly, until the terminal demasks the CRC part of the received control information item with its own terminal ID, the terminal cannot determine whether or not the control information item is intended for the terminal. In this blind-determination, if the result of demasking the CRC part indicates that the CRC operation is OK, the control information item is determined as being intended for the terminal.
Moreover, in 3GPP LTE, Automatic Repeat Request (ARQ) is applied to downlink data to terminals from a base station. More specifically, each terminal feeds back a response signal indicating the result of error detection on the downlink data to the base station. Each terminal performs a CRC on the downlink data and feeds back Acknowledgment (ACK) when CRC=OK (no error) or Negative Acknowledgment (NACK) when CRC=Not OK (error) to the base station as a response signal. An uplink control channel such as Physical Uplink Control Channel (PUCCH) is used to feed back the response signal (i.e., ACK/NACK signal (hereinafter, may be referred to as “A/N,” simply)).
The control information to be transmitted from a base station herein includes resource assignment information including information on resources assigned to the terminal by the base station. As described above, PDCCH is used to transmit this control information. The PDCCH includes one or more L1/L2 control channels (L1/L2 CCH). Each L1/L2 CCH consists of one or more Control Channel Elements (CCE). More specifically, a CCE is the basic unit used to map the control information to a PDCCH. Moreover, when a single L1/L2 CCH consists of a plurality of CCEs (2, 4 or 8), a plurality of contiguous CCEs starting from a CCE having an even index are assigned to the L1/L2 CCH. The base station assigns the L1/L2 CCH to the resource assignment target terminal in accordance with the number of CCEs required for indicating the control information to the resource assignment target terminal. The base station maps the control information to physical resources corresponding to the CCEs of the L1/L2 CCH and transmits the mapped control information.
In addition, CCEs are associated with component resources of a PUCCH (hereinafter, may be referred to as “PUCCH resource”) in a one-to-one correspondence. Accordingly, a terminal that has received an L1/L2 CCH identifies the component resources of PUCCH that correspond to the CCEs forming the L1/L2 CCH and transmits a response signal to the base station using the identified resources. However, when the L1/L2 CCH occupies a plurality of contiguous CCEs, the terminal transmits the response signal to the base station using a PUCCH component resource corresponding to a CCE having a smallest index among the plurality of PUCCH component resources respectively corresponding to the plurality of CCEs (i.e., PUCCH component resource associated with a CCE having an even numbered CCE index). In this manner, the downlink communication resources are efficiently used.
As illustrated in FIG. 1, a plurality of response signals transmitted from a plurality of terminals are spread using a Zero Auto-correlation (ZAC) sequence having the characteristic of zero autocorrelation in time-domain, a Walsh sequence and a discrete Fourier transform (DFT) sequence, and are code-multiplexed in a PUCCH. In FIG. 1, (W0, W1, W2, W3) represent a length-4 Walsh sequence and (F0, F1, F2) represent a length-3 DFT sequence. As illustrated in FIG. 1, ACK or NACK response signals are primary-spread over frequency components corresponding to 1 SC-FDMA symbol by a ZAC sequence (length-12) in frequency-domain. More specifically, the length-12 ZAC sequence is multiplied by a response signal component represented by a complex number. Subsequently, the ZAC sequence serving as the response signals and reference signals after the primary-spread is secondary-spread in association with each of a Walsh sequence (length-4: W0-W3 (may be referred to as Walsh Code Sequence)) and a DFT sequence (length-3: F0-F3). To put it more specifically, each component of the signals of length-12 (i.e., response signals after primary-spread or ZAC sequence serving as reference signals (i.e., Reference Signal Sequence) is multiplied by each component of an orthogonal code sequence (i.e., orthogonal sequence: Walsh sequence or DFT sequence). Moreover, the secondary-spread signals are transformed into signals of length-12 in the time-domain by inverse fast Fourier transform (IFFT). A CP is added to each signal obtained by IFFT processing, and the signals of one slot consisting of seven SC-FDMA symbols are thus formed.
The response signals from different terminals are spread using ZAC sequences each corresponding to a different cyclic shift value (i.e., index) or orthogonal code sequences each corresponding to a different sequence number (i.e., orthogonal cover index (OC index)). An orthogonal code sequence is a combination of a Walsh sequence and a DFT sequence. In addition, an orthogonal code sequence is referred to as a block-wise spreading code in some cases. Thus, base stations can demultiplex the code-multiplexed plurality of response signals using the related art despreading and correlation processing (see, NPL 4).
However, it is not necessarily true that each terminal succeeds in receiving a downlink assignment control signal because the terminal performs blind-determination in each subframe to find a downlink assignment control signal intended for the terminal. When the terminal fails to receive the downlink assignment control signals intended for the terminal on a certain downlink component carrier, the terminal would not even know whether or not there is downlink data intended for the terminal on the downlink component carrier. Accordingly, when a terminal fails to receive the downlink assignment control signal intended for the terminal on a certain downlink component carrier, the terminal generates no response signal for the downlink data on the downlink component carrier. This error case is defined as discontinuous transmission of ACK/NACK signal (DTX of response signal) in the sense that the terminal transmits no response signal.
In 3GPP LTE systems (may be referred to as “LTE system,” hereinafter), base stations assign resources to uplink data and downlink data, independently. For this reason, in the 3GPP LTE system, terminals (i.e., terminals compliant with LTE system (hereinafter, referred to as “LTE terminal”)) encounter a situation where the terminals need to transmit uplink data and response signals for downlink data simultaneously in the uplink. In this situation, the response signals and uplink data from the terminals are transmitted using time-division multiplexing (TDM). As described above, the single carrier properties of transmission waveforms of the terminals are maintained by the simultaneous transmission of response signals and uplink data using TDM.
In addition, as illustrated in FIG. 2, the response signals (i.e., “A/N”) transmitted from each terminal partially occupy the resources assigned to uplink data (i.e. Physical Uplink Shared CHannel (PUSCH) resources) (i.e., response signals occupy some SC-FDMA symbols adjacent to SC-FDMA symbols to which reference signals (RS) are mapped) and are thereby transmitted to a base station in time-division multiplexing (TDM). In FIG. 2, however, “subcarriers” in the vertical axis of the drawing are also termed as “virtual subcarriers” or “time contiguous signals,” and “time contiguous signals” that are collectively inputted to a discrete Fourier transform (DFT) circuit in a SC-FDMA transmitter are represented as “subcarriers” for convenience. More specifically, optional data of the uplink data is punctured due to the response signals in the PUSCH resources. Accordingly, the quality of uplink data (e.g., coding gain) is significantly reduced due to the punctured bits of the coded uplink data. For this reason, base stations instruct the terminals to use a very low coding rate and/or to use very large transmission power so as to compensate for the reduced quality of the uplink data due to the puncturing.
Meanwhile, the standardization of 3GPP LTE-Advanced for realizing faster communications than 3GPP LTE has been carried out. 3GPP LTE-Advanced systems (may be referred to as “LTE-A system,” hereinafter) follow LTE systems. 3GPP LTE-Advanced is expected to introduce base stations and terminals capable of communicating with each other using a wideband frequency of 40 MHz or greater to realize a downlink transmission rate up to 1 Gbps or above.
In the LTE-A system, in order to simultaneously achieve backward compatibility with the LTE system and ultra-high-speed communication several times faster than transmission rates in the LTE system, the LTE-A system band is divided into “component carriers” of 20 MHz or below, which is the bandwidth supported by the LTE system. In other words, the “component carrier” is defined herein as a band having a maximum width of 20 MHz and as the basic unit of communication band. Moreover, in a Frequency Division Duplex (FDD) system, “component carrier” in downlink (hereinafter, referred to as “downlink component carrier”) is defined as a band obtained by dividing a band according to downlink frequency bandwidth information in a BCH broadcasted from a base station or as a band defined by a distribution width when a downlink control channel (PDCCH) is distributed in the frequency domain. In addition, “component carrier” in uplink (hereinafter, referred to as “uplink component carrier”) may be defined as a band obtained by dividing a band according to uplink frequency band information in a BCH broadcasted from a base station or as the basic unit of a communication band of 20 MHz or below including a Physical Uplink Shared CHannel (PUSCH) in the vicinity of the center of the bandwidth and PUCCHs for LTE on both ends of the band. In addition, the term “component carrier” may be also referred to as “cell” in English in 3GPP LTE-Advanced. In addition, the term “component carrier” may be also referred to as “CC(s)” as an abbreviation.
In a Time Division Duplex (TDD) system, a downlink component carrier and an uplink component carrier are in the same frequency band, and downlink communication and uplink communication are realized by time-division switching between uplink and downlink. Therefore, in the case of the TDD system, the downlink component carrier can also be expressed as “downlink communication timing in the component carrier.” The uplink component carrier can also be expressed as “uplink communication timing in the component carrier.” The switching between the downlink component carrier and the uplink component carrier is based on the UL-DL Configuration, as shown in FIG. 3. In the UL-DL Configuration shown in FIG. 3, the timing of downlink communication (DL: Downlink) and uplink communication (UL: Uplink) per one frame (10 msec) in units of a subframe (that is, 1 msec unit) is set. The UL-DL Configuration can build a communication system that can flexibly respond to the requests of throughput for uplink communication and throughput for downlink communication by changing the subframe ratio of uplink communication and downlink communication. For example, FIG. 3 shows UL-DL Configurations (Config 0 to Config 6) whose subframe ratios of uplink communication and downlink communication are different. In addition, in FIG. 3, a downlink communication subframe is expressed as “D,” an uplink communication subframe is expressed as “U,” and a special subframe is expressed as “S.” Here, the special subframe is a subframe at the time of switching from a downlink communication subframe to an uplink communication subframe. In addition, in the special subframe, downlink data communication may be performed similar to the downlink communication subframe. In addition, in each UL-DL Configuration shown in FIG. 3, subframes (20 subframes) of two frames are divided into subframes (“D” and “S” in the upper stage) used in downlink communication and subframes (“U” in the lower stage) used in uplink communication and are thus expressed in two stages. In addition, as shown in FIG. 3, results (ACK/NACK) of error detection on downlink data are reported in the fourth uplink communication subframe from the subframe to which the downlink data is assigned, or an uplink communication subframe after the fourth subframe.
In the LTE-A system, communication using a band obtained by bundling some component carriers, a so-called Carrier aggregation (CA) is supported. In addition, although the UL-DL Configuration can be set for each component carrier, a terminal supporting the LTE-A system (hereinafter, referred to as “LTE-A terminal”) is designed on the assumption that the same UL-DL Configuration is set for a plurality of component carriers.
FIGS. 4A and 4B are diagrams for explaining asymmetric Carrier aggregation applied to an individual terminal and the control sequence.
As illustrated in FIG. 4B, a configuration in which carrier aggregation is performed using two downlink component carriers and one uplink component carrier on the left is set for terminal 1, while a configuration in which the two downlink component carriers identical with those used by terminal 1 are used but uplink component carrier on the right is used for uplink communication is set for terminal 2.
Referring to terminal 1, a base station (i.e., a base station supporting the LTE-A system (hereinafter, referred to as “LTE-A base station”)) and an LTE-A terminal included in the LTE-A system transmit and receive signals to and from each other in accordance with the sequence diagram illustrated in FIG. 4A. As illustrated in FIG. 4A, (1) terminal 1 is synchronized with the downlink component carrier on the left when starting communications with the base station and reads information on the uplink component carrier paired with the downlink component carrier on the left from a broadcast signal called system information block type 2 (SIB2). (2) Using this uplink component carrier, terminal 1 starts communications with the base station by transmitting, for example, a connection request to the base station. (3) Upon determining that a plurality of downlink component carriers need to be assigned to the terminal, the base station instructs the terminal to add a downlink component carrier. However, in this case, there is no increase in the number of uplink component carriers, and terminal 1, which is an individual terminal, starts asymmetric carrier aggregation.
In addition, in the LTE-A system to which carrier aggregation is applied, a terminal may receive a plurality of pieces of downlink data on a plurality of downlink component carriers at a time. In LTE-A, there are channel selection (also referred to as “multiplexing”), bundling and a discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) format as a method of transmitting a plurality of response signals for the plurality of pieces of downlink data. In channel selection, not only symbol points used for response signals, but also the resources to which the response signals are mapped are varied in accordance with the pattern for results of the error detection on the plurality of pieces of downlink data by the terminal. Compared with channel selection, in bundling, ACK or NACK signals generated according to the results of error detection on the plurality of pieces of downlink data are bundled (i.e., bundled by calculating a logical AND of the results of error detection on the plurality of pieces of downlink data, provided that ACK=1 and NACK=0), and response signals are transmitted using one predetermine resource by the terminal. In transmission using the DFT-S-OFDM format, a terminal jointly encodes (i.e. joint coding) the response signals for the plurality of pieces of downlink data and transmits the coded data using the format (see, NPL 5). For example, a terminal may feedback the response signals (i.e., ACK/NACK) using channel selection, bundling or DFT-S-OFDM according to the number of bits for a pattern for results of error detection. Alternatively, a base station may previously configure the method of transmitting the response signals.
More specifically, channel selection is a technique that varies not only the phase points (i.e., constellation points) for the response signals but also the resources used for transmission of the response signals (may be referred to as “PUCCH resource,” hereinafter) on the basis of whether the results of error detection on the plurality of pieces of downlink data for each downlink component carrier received on the plurality of downlink component carriers (up to two downlink component carriers) are each an ACK or NACK as illustrated in FIG. 5. Meanwhile, bundling is a technique that bundles ACK/NACK signals for the plurality of pieces of downlink data into a single set of signals and thereby transmits the bundled signals using one predetermined resource (see, NPLs 6 and 7). Hereinafter, the set of the signals formed by bundling ACK/NACK signals for a plurality of pieces of downlink data into a single set of signals may be referred to as “bundled ACK/NACK signals”.
The following two methods are considered as a possible method of transmitting response signals in uplink when a terminal receives downlink assignment control information via a PDCCH and receives downlink data.
One of the methods is to transmit response signals using a PUCCH resource associated in a one-to-one correspondence with a control channel element (CCE) occupied by the PDCCH (i.e., implicit signaling) (hereinafter, method 1). More specifically, when DCI intended for a terminal served by a base station is allocated in a PDCCH region, each PDCCH occupies a resource consisting of one or a plurality of contiguous CCEs. In addition, as the number of CCEs occupied by a PDCCH (i.e., the number of aggregated CCEs: CCE aggregation level), one of aggregation levels 1, 2, 4 and 8 is selected according to the number of information bits of the assignment control information or a propagation path condition of the terminal, for example.
The other method is to previously report a PUCCH resource to each terminal from a base station (i.e., explicit signaling) (hereinafter, method 2). To put it differently, each terminal transmits response signals using the PUCCH resource previously reported by the base station in method 2.
In addition, as shown in FIG. 5, the terminal transmits a response signal using one of the two component carriers. The component carrier used to transmit such a response signal is called a Primary Component Carrier (PCC) or a Primary Cell (PCell). In addition, the other component carrier is called a Secondary Component Carrier (SCC) or a Secondary Cell (SCell). For example, the PCC (PCell) is a component carrier used to transmit broadcast information (for example, SIB2 (System Information Block type2)) regarding a component carrier used to transmit the response signal.
In method 2, PUCCH resources common to a plurality of terminals (e.g., four PUCCH resources) may be previously reported to the terminals from a base station. For example, terminals may employ a method to select one PUCCH resource to be actually used, on the basis of a transmit power control (TPC) command of two bits included in DCI in SCell. In this case, the TPC command is called an ACK/NACK resource indicator (ARI). Such a TPC command allows a certain terminal to use an explicitly signaled PUCCH resource in a certain frame while allowing another terminal to use the same explicitly signaled PUCCH resource in another subframe in the case of explicit signaling.
Meanwhile, in channel selection, a PUCCH resource in an uplink component carrier associated in a one-to-one correspondence with the top CCE index of the CCEs occupied by the PDCCH indicating the Physical Downlink Shared CHannel (PDSCH) in PCC (PCell) (i.e., PUCCH resource in PUCCH region 1 in FIG. 5) is assigned (implicit signaling).
Next, a description will be provided regarding ARQ control using channel selection when the asymmetric carrier aggregation described above is applied to terminals with reference to FIGS. 5 and 6.
A component carrier group (may be referred to as “component carrier set” in English) consisting of component carrier 1 (PCell), component carrier 2 (SCell) and uplink component carrier 1 is configured for terminal 1 as illustrated in FIG. 5. In this case, after downlink resource assignment information is transmitted via a PDCCH of each of component carriers 1 and 2, downlink data is transmitted using the resource corresponding to the downlink resource assignment information.
In addition, in channel selection, response signals indicating the results of error detection on a plurality of pieces of downlink data in the component carrier 1 (PCell) and the results of error detection on a plurality of pieces of downlink data in the component carrier 2 (SCell) are mapped to the PUCCH resources included in the PUCCH region 1 or the PUCCH region 2. In addition, the terminal uses either two types of phase points (Binary Phase Shift Keying (BPSK) mapping) or four types of phase points (Quadrature Phase Shift Keying (QPSK) mapping) as a response signal. That is, in channel selection, it is possible to express the patterns of the results of error detection on a plurality of pieces of downlink data in the component carrier 1 (PCell) and the results of error detection on a plurality of pieces of downlink data in the component carrier 2 (SCell) using the combination of PUCCH resources and phase points.
Here, a method of mapping the patterns of results of error detection when there are two component carriers (when there are one PCell and one SCell) in the TDD system is shown in FIG. 6A.
In addition, in FIG. 6A, a case is assumed in which a transmission mode is set to one of the following transmission modes (a), (b), and (c).
(a) Transmission mode in which each component carrier supports only downlink one-CW transmission
(b) Transmission mode in which one component carrier supports only downlink one-CW transmission and the other component carrier supports up to downlink two-CW transmission
(c) Transmission mode in which each component carrier supports up to downlink two-CW transmission
In addition, in FIG. 6A, a case is assumed in which a number M, which indicates the results of error detection for how many downlink communication subframes (hereinafter, described as DownLink (DL) subframes; “D” or “S” shown in FIG. 3) per component carrier need to be reported to the base station in one uplink communication subframe (hereinafter, described as UpLink (UL) subframes; “U” shown in FIG. 3), is set to one of the following settings (1) to (4). For example, in Config 2 shown in FIG. 3, since the results of error detection of four DL subframes is reported to the base station in one UL subframe, M=4 is set.
(1) M=1
(2) M=2
(3) M=3
(4) M=4
That is, FIG. 6A shows a method of mapping the patterns of error detection results when the above-described (a) to (c) and the above-described (1) to (4) are combined. In addition, the value of M changes with the UL-DL Configuration (Config 0 to Config 6) and the subframe number (SF#0 to SF#9) in one frame, as shown in FIG. 3. In addition, in Config 5 shown in FIG. 3, M=9 is set in the subframe (SF) #2. In this case, however, in the TDD system of LTE-A, the terminal reports the error detection result using, for example, a DFT-S-OFDM format without applying channel selection. Therefore, in FIG. 6A, Config 5 (M=9) is not included in the above-described combination.
In the case of (1), the number of patterns of error detection results is 22×1=4 patterns, 23×1=8 patterns, and 24×1=16 patterns in order of (a), (b), and (c). In the case of (2), the number of patterns of error detection results is 22×2=8 patterns, 23×2=16 patterns, and 24×2=32 patterns in order of (a), (b), and (c). The same is true for the cases of (3) and (4).
Here, a case where the phase difference between the phase points mapped in one PUCCH resource is at least 90° (that is, a case where up to 4 patterns per one PUCCH resource are mapped) is assumed. In this case, the number of PUCCH resources required for mapping all patterns of error detection results is 24×4÷4=16 in cases of (4) and (c) where the number of patterns of error detection results becomes a maximum (24×4=64 patterns), which is not practical. Therefore, in the TDD system, the amount of information of error detection results is made to intentionally be missing by bundling the error detection results in a spatial domain and further in a time domain when necessary. In this manner, the number of PUCCH resources required for the reporting of error detection result patterns is limited.
In the TDD system of LTE-A, in the case of (1), the terminal maps the error detection result patterns of 4 patterns, 8 patterns, and 16 patterns to two, three, and four PUCCH resources, respectively, in order of (a), (b), and (c) without bundling the error detection results (Step 3 in FIG. 6A). That is, the terminal reports a 1-bit error detection result per component carrier for which a transmission mode (non-MIMO) that supports only one-CW (codeword) transmission in the downlink is set, and reports a 2-bit error detection result per component carrier for which a transmission mode (MIMO) that supports up to two-CW transmission in the downlink is set.
In the TDD system of LTE-A, also in cases of (2) and (a), the terminal maps the error detection result patterns of 8 patterns to four PUCCH resources without bundling the error detection results (Step 3 in FIG. 6A). In this case, the terminal reports a 2-bit error detection result per one downlink component carrier.
In the TDD system of LTE-A, also in cases of (2) and (b) (also the same for (2) and (c)), the terminal bundles (spatially bundles) (Step 1 in FIG. 6A) error detection results of the component carrier for which a transmission mode that supports up to two-CW transmission in the downlink is set, in a spatial domain. In the spatial bundling, for example, when an error detection result for at least one CW of error detection results of two CWs is NACK, the error detection result after the spatial bundling is determined to be NACK. That is, in the spatial bundling, logical AND (Logical And) is taken for the error detection results of two CWs. Then, the terminal maps an error detection result pattern after spatial bundling (8 patterns in cases of (2) and (b), and 16 patterns in cases of (2) and (c)) to four PUCCH resources (Step3 in FIG. 6A). In this case, the terminal reports a 2-bit error detection result per one downlink component carrier.
In the TDD system of LTE-A, also in cases of (3) or (4) and (a), (b), or (c), the terminal performs bundling in a time domain (time-domain bundling) after spatial bundling (Step1) (Step2 in FIG. 6A). Then, the terminal maps the error detection result patterns after time-domain bundling to four PUCCH resources (Step3 in FIG. 6A). In this case, the terminal reports a 2-bit error detection result per one downlink component carrier.
Next, an example of a specific mapping method is shown using FIG. 6B. FIG. 6B shows examples when there are two downlink component carriers (one PCell and one SCell) and when “(c) transmission mode in which each component carrier supports up to downlink two-CW transmission” is set and “(4) M=4”.
In FIG. 6B, the error detection results of PCell are (ACK(A), ACK), (ACK, ACK), (NACK(N), NACK), and (ACK, ACK) in order of (CW0, CW1) in four DL subframes (SF1 to SF4). In the PCell shown in FIG. 6B, since M=4, the terminal performs spatial bundling of these in Step1 in FIG. 6A (portions surrounded by the solid lines in FIG. 6B). As a result of spatial bundling, ACK, ACK, NACK, and ACK are obtained in this sequence in four DL subframes of the PCell shown in FIG. 6B. In addition, in Step2 in FIG. 6A, the terminal performs time-domain bundling for the 4-bit error detection result pattern (ACK, ACK, NACK, ACK) after spatial bundling obtained in Step1 (portion surrounded by the dotted line in FIG. 6B). As a result, in the PCell shown in FIG. 6B, a 2-bit error detection result of (NACK, ACK) is obtained.
The terminal performs spatial bundling and time-domain bundling similarly for the SCell shown in FIG. 6B, thereby obtaining a 2-bit error detection result of (NACK, NACK).
In addition, in Step 3 in FIG. 6A, the terminal puts together 2-bit error detection result patterns of the PCell and the SCell after time-domain bundling into 4-bit error detection result patterns (NACK, ACK, NACK, NACK) by combining them in order of the PCell and the SCell. The terminal determines a PUCCH resource (in this case, h1) and a phase point (in this case, −j) using a mapping table showing in Step3 in FIG. 6A for the 4-bit error detection result pattern.